The Ionic Bond B. A. Rowland 53750/53760 Electron Shielding Please see Lecture Notes for “The Periodic Table and Atomic Configurations”. Formulas for Ionic Compounds In order to discuss ionic bond strength, we will need to be able to assign charges to the individual ions in an ionic compound. There are two possible ways to accomplish this. The first is through the use of electronic configurations. You can write the electronic configuration for the atom at hand and then remove valence electrons (for positive ions) or add electrons to the valence orbitals (for negative ions) until the ion reaches a noble gas configuration. This entails much work, and a simpler method for doing this involves using the Periodic Table. Any ion from group 1 will have a (+1) charge, and any ion from group 2 will have a (+2) charge. For those using an IUPAC Periodic Table the situation changes. For group 13 (3 on non-IUPAC tables) the charge is (+3), group 14 (4) would be (+/- 4), group 15 (5) would be (-3), group 16 (6) would be (-2), group 17 (7) would be (-1), and group 18 (8) would be (0). Note that this scheme will NOT work for transition metal elements—their charge must usually explicitly be given. Reminder: Ionic Radius Please see Lecture Notes for “The Periodic Table and Atomic Configurations”. Reminder: Coulomb’s Law Remember that charged particles (electrons and protons, positive and negative ions) can interact through electrostatic interactions. The force between the above mentioned oppositely charged particles is described by Coulomb’s Law . We will use a modified form of Coulomb’s law to calculate the lattice energy

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